Analysis systems which allow individual parameters in sample liquids to be determined have been known for a long time, and many versions of them are commercially available. Particularly for the field of medical diagnosis and environmental analysis, appliances are offered which can also be operated by personnel with less training. Systems such as these which operate without the use of liquid reagents and in which, in general, no preparation of the sample material, or at least no complex preparation of the sample material, is required, are simple to operate. A “dry chemistry” has been developed for these so-called quick tests, in which the liquid contained in the sample liquid is used on its own as a solvent.
By way of example, systems for determination of glucose in the blood are in use, in which the patient places a small amount of blood on a test element, and carries out the measurement using an appliance which is simple to operate.
Conventional evaluation appliances have an opening, for example a slot, into which a test element can be inserted, typically by hand. Guide elements ensure that a test element is inserted in the intended orientation. The appliance typically has design features in order to ensure the desired positioning of the test element.
There are various forms of test elements. Those known include, for example, substantially small rectangular sheets, which are also referred to as strips, in whose center a multilayer test area is located. Diagnostic test elements which are in the form of strips are also referred to as test strips. Capillary test elements are known from the prior art, for example from WO 99/29429, for three-dimensional separation of a detection zone and a sample application point on a test element.
A large number of methods are known for measurement of the concentration of analytes, for example of glucose in a blood sample. Methods such as these are normally subdivided into one of two categories: optical methods or electrochemical methods.
Optical methods are based on color changes which produce an indication in the course of the verification reaction when the analytes to be determined are present. The color change which occurs on the test element can be detected by reflection-photometry. A transmission measurement is likewise possible, but in some cases necessitates the use of transparent test strips.
Electrochemical methods for determination of the concentration of an analyte are based, for example, on amperometry or coulometry. Methods such as these are known, for example, from the documents U.S. Pat. No. 4,654,197, EP 0 505 475 B1, US 2002/0057993 A1, EP 1 321 769 A1, WO 03/083469 A2 or U.S. Pat. No. 5,108,564. Electrical signals must be transmitted between the test element and the evaluation appliance in order to carry out the electrochemical analysis. A test element which has been introduced into an evaluation appliance therefore has to have electrical contact made with it in the evaluation appliance, with the aid of an electrical connection system.
Test elements which are used in the prior art are generally designed in layers and have contact surfaces in the form of thin metallic or otherwise conductive layers, in order to make electrical contact. In the case of evaluation appliances which are commercially available at the moment, the electrical contact elements of the appliance slide over the contact surfaces during the insertion of the test element, and can damage it in the process. Furthermore, material accumulations occur at the electrical contact elements of the evaluation appliance. Reliable contact can therefore not be ensured.